SOZ virgin needs help!

[Lenin]

OK, I've given in. After a month of reading the Pass Labs forum (I don't know why, but I'd ignored it for months previously), I've decided to build SOZ.

I'm determined to build something that will not fall foul of the houshold authorities (my wife), nor permanently scar my inquisitive children. I've sketched out internal layouts for the amp and rekon I'm looking at the following (stereo) specification:

1.2KVA transformer
300,000u resevoir capacitance
4x 0.12 deg C/W heatsinks

Before I start commiting myself to a SOZ project far too low on one of these 3 parameters, I'd really appreciate some advice from you guys on just how far out I am - maybe with some rough and ready rules of thumb for me to bear in mind.

Thanks in advance!

[paulb]

You didn't mention the output power you're going for. The SOZ is adjustable by its power supply voltage.

[ralf]

in pass sites you can see with how much Voltage of your transformer you get how much on Power.

With your Heatsinks i guess you can drive the SOZ about 20watts.

Nevertheless, i`m in Soz/Bosoz Project actally, myself and they work in eyaluatio since some month.
The Combination Soz/Bosoz is outstanding good in sound, depending on the parts -quality you use.

regards,

Ralf

[mefinnis]

I'm determined to build something that will not fall foul of the houshold authorities (my wife)

Then the SOZ would be an odd choice, or, you have a very accommodating wife

Does she realise just how large and hot this will be ??

cheers, mark

[ralf]

...he`s right,

Ralf

[Lenin]

Your right, I didn't mention what output power I'm going for. From what I've picked up from threads on the forum, the "I've built a 50wpc SOZ" boys have got it all wrong, as 15 - 20w sounds fine (or possibly better - !) and provides enough power for real world speakers.

With this in mind, I'm aiming for about 20w.

As far as guidance from pass sites is concerned, I've not been able to find any! The Pass DIY site has info on Zen-lightenment only (at least it did yesterday, maybe the site's SOZ info is being updated or something - I don't know). With occasional references to power supply formulas popping up all over the place (but no links posted as to where!) you can imagine how fustrated I am!

Any danger of posting some links here for me guys? (I'm particularly worried that the transformer may just be too small)

Oh, one final newbie question (thanks for your patience). Isn't the rail voltage for SOZ a touch low? Wouldn't cranking up the rail voltage help to increase power output? (Excuse my ignorance!)

Finally, OK, SOZ is hardly a good choice for someone aiming to maintain domestic harmony, but there lies the challenge! Let me explain. I've looked at galleries featuring completed SOZ projects and I have to say, I really feel that people have generally been lazy with their implementaions, relying on the fact that the design needs to dissapate huge amounts of heat to justify amplifiers the size of small fridges in their living rooms. If my wife really were that accomodating (or just plain mad) I suppose a 1 and a 1/2 foot square anodized radiator would be fine. Unfortunately, she isn't.

So what I'm building is a pair of 'half width' 20w SOZ monoblocks. Dimensions: 5 in x 8in x 14 in (h x w x d) (Yes, you read that right). Sat together, the monoblocks should take up about the same space as an average CD player - about one third the size of typical SOZ implementations I've seen.

Now guys I can almost hear some of you scoffing as I type this info, finding it hard to believe that some idiot honestly believes it is possible to buils a SOZ the size of a CD player, but I'm happy to provide more info on just how I'm doing it.

[Nelson Pass]

Get yourself a Variac for this, and you can have your
cake and eat it too.

[Lenin]

I messed up on the dimensions of the SOZ monoblocks I'm pulling together.

Dimensions should read: 4in x 8in x 14in.

[BrianGT]

That seems like too small of a form factor to put the monoblock 20W soz in. Reading over the article on PassDIY, it appears that the total dissipitation of the 20W zen would be 500W. That seems like it would require a lot of heatsinking, definately more then you are considering.

How were you planning on setting up the heatsinks? One for the resistors and another for the transistors?

I think that the best idea would be to get a variac and at what wattage you can obtain reasonable temperatures. I would imagine that you would have to make it 10W, from seeing others SOZ amplifiers.

I guess it just depends on how much of the 4"x8"x14" is heatsink.

--
Brian
gte619j@prism.gatech.edu

[Lenin]

Surely I'm ok on heatsinking?

Even at 500w total disappation for a 20wpc SOZ (I'm presuming that includes the power resitors dissapation requirements). Four 0.12 c/w heatsinks should be more than adequate.

Splitting the 500w dissapation load across the 4 heatsinks to give 125w per heatsink, were looking at a measly 15 degree temperature rise on each heatsink. (0.12 deg c/w x 125w).
Have I got this right?

OK, I've not considered the allowances that need to be made for thermal interface issues, the type of thermal interface material etc, etc... but hey, let me say it again, we are looking at just a 15 degree temperature rise on each heatsink! This will be one cool running 20w SOZ!

I'm far more worried about the power supply. If I'm to stick to my 'dinky monoblock minatures' idea, I'm really stuck on 600VA and 300,000u per channel. Is this on the wimpy side?

HELP!